Process and material for the manufacture of etched printing plates



Dec. 7, 1965 A. RoTT ETAL 3,222,174 PROCESS AND MATERIAL FOR THEMANUFACTURE OF ETCHED PRINTING PLATES Filed 001;. 31, 1960 ATTORNEYSUnited States Patent i PRCESS AND MATERIAL `FRTH'E MANUFAC- The presentinvention relates to etched printing plates, and more particularly tophotographic stripping material used for the manufacture of suchprinting plates.

The processes for the manufacture of etched metal printing plates bymeans of photographically obtained gelatin images manufactured and`hardened on stripping lm are generally known. This stripping lm mainlyconsists of a light-sensitive and unhardened gelatino silver halideemulsion layer coated on a thin -cellulose ester lilm, called apermanent support, which in its turn is applied in such a way to athicker transparent film support, called a temporary support, that itcan be stripped olf. For this temporary support the raw materials usedfor the manufacture of photographic supports, eg., cellulose esters,polyesters, polycarbonates, polysulfonates and polyamides can be used. l

In these processes, the following treatments for instance are applied:

(l) The light-sensitive layerof the stripping film is exposed through ascreen and a diapositive. l

(2) The light-sensitive layer is treated with a tanning developer and,as the case may be, fixed, washed and dried.

(3) The treated stripping lm is transferred onto the wetted metalsurfa-ce byvpressing with a roller.

(4) The temporary support is removed.

(5 The permanent support is removed.

v(6) The non-hardened gelatin is washed away wit warm water and thegelatin relief obtained is dried.

(7) The metal surface is etched.

The removal of the temporary support is effected easily by strippingolf; the removal of the permanent support, however, is a delicatetreatment which easily leads to failures.

For the removal of the permanent support, the following conventionaltechniques are employed:

(a) The layer serving as permanent support and usually consisting ofnitrocellulose is dissolved with acetone or with another solvent, such`as described in U.S. Patent 2,650,878. The control of the completeremoval of such nitrocellulose permanent support, however, is diicultand if said removal is not properly accomplished this may lead toirregularities in the subsequent treatment of the emulsion layer withwarm water.

(b) The permanent support Vconsisting of nitrolcellulose is allowed toswell in methanol or ethanol and is then treated with warm water wherebyit can be stripped off since the subjacent unhardenedemulsion melts off.

The penetration of `sufficient water for enabling this melting olfrequires, however, much time and a rather high temperature of the water.p

A particular d-iliculty for removing the permanent support arises if inthe previous treatment the hardening of the image layer has reached thepermanent support. In order to avoid this evil, it is known to apply aspecial low-melting gelatin layer between the light-sensitive layer andthe permanent support (Belgian patent specification 564,233).

Now we have found that the permanent support can be removedfaster andwithout supply of heat by stripping u 3,222,174 Patented Dec. 7, 1965 itas a coherent membrane which is `done by wetting this support for a fewseconds with armixture containing a solvent for this support and a less,volatile nonsolvent and then evaporating the mixture in the air for afew seconds.

The accompanying drawing shows a sectional View of a stripping filmwhich is suitable for the application of the process according to thepresent invention and wherein the layers represent:`

(1) an anti-halation layer (2) a subbing layer (3) a temporary support(4) astripping layer (5) a permanent or thin support -of cellulose estercontaining 5-40 plast-icizr (6) asubbing layer (7)alightfsensitiveemulsion,

Although the exact mechanism of this surprising effect is not quiteknown, it can be admitted that the act-ion of the mixture of the solventand the non-solvent (e.g. acetone and water) occurs asfollows: duringthe first seconds of the action of the acetone lon the nitrocellulose,the molecules of the latter are solvated by the acetone molecules, soAthat the thin nitrocellulose layer obtains a jellylike consistency.`Duringv the subsequent short drying period, the acetone concentrationfalls together with thel degree of solvation.. From acertain moment theconsistncy of the nitrocellulose suddenly changes from jellylike into amore coherent and half-solid state which perhaps means that the` acetoneis no longer held by solvation but by absorption by the nitrocellulose.This transition is quite sharp, `occurs practically discontinuously andis accelerated by the cooling action of the acetone evaporation. Theusually occurring white coloring of the nitrocellulose i-s explained bythe precipitation of the latter caused by the Water present. By thestrong swelling and ilocculati-on, the permanent support consisting ofnitrocellulose has lost contact with the subjacent gelatin layer and canbe stripped therefrom very easily. A

The new process is more reliable if an adapted amount of a swellingagent for the permanent support, such as e.g. ethanol, is added to themixture of solventand nonsolvent used. Hereby the time schedule forstripping off the permanent support is considerably widened so that ondrying there is no risk that the permanent support will become adheredagain to the gelatin.

`In order to expedite this process care should be taken that onmanufacturing the material herein applied, the

, cellulose ester lm serving as permanent support contains a relatively`considerable amount of plasticizer; for this purpose a pla-sticizer inan amount ranging from 5 to 40% but preferably of at least 10% can beadded to the casting composition from which the permanent support iscast, or, if the temporary support consists of a cellulose ester, asupport can be used which contains a large amount of plasticizer whichafterwards can pass into the permanent support by diffusion.

Suitable plasticizers are eng. triphenylphosphate, tricresylphosphate,Palatino] A, Palatinol M, Palatino O (trade names for diethylphthalate,dimethylphthalate, resp, di(methoxyethyl)-phthalate, marketed byBadische Anilin- & Soda-Fabrik A.G., Ludwigshafen/Rh), Santicizer (tradename for tolyldiphenylphosphate, marketed by Monsanto Chemical Company,St. Louis, Mo., U.S.A.), Sipalin (trade name for dicyclohexyl ad-ipatemarketed by Deutsche Hydrierwerke A.G., Dusseldorf-Holthausen) andTriacetin (trade name for glycerine triacetate marketed byFarbenfabriken Bayer A.G., Leverkusen). The thickness of the subbinglayer between thevernulsion layer and the permanent support mustbe verythin if nomplasticizer is incorporated in the permanent support. Thuse.g. for a temporary cellulose 3 ester support and for a permanentsupport which coritains no plasticizer, this subbirig layer r'iust notbe thicker than 0.2,u.. If, however, in the permanent support arelatively large amount of plasticizer is incorporated, the

thickness of the aforesaid subbing layer is not as critical. Preferably,however, a thickness smaller than 0.4/1. is used. In the new process nowarm water is needed for the removal of the permanent support (treatment5). Since it is also possible to exclude the use of warm water intreatment 6 by carrying out the Washing away of the non-hardened gelatinparts (treatment 6) with peptizing solutions such as aqueous solutionsof ammonium bromide, sodium salicylate, potassium rhodanide or urea, orwith proteolytic enzymes, the application of the process acording to thepresent invention enables to exclude before etching (treatment 7) theprolonged cooling of the cppr cylinder serving as printingplate. In thisway the whole process of the'n-ariufctdre of printing plates isconsiderably shortened. i

The following examples illustrate the invention without limiting,however, the scope thereof.

EXAMPLE l Materal.-A stripping lm is manufactured by applyingsuccessively the following layers onto the front side of a cellulosetriacetate support (I) of a thickness of 0.15 mm., the rear side ofwhich is provided with the usual photographic subbing (II) andanti-halation layers (III).

(1) A stripping layer (IV) from the following composition:

Nitrocellulose g 8 Ethylcellulose g 4 Methanol cc 700 Acetone cc 250n-Butanol cc 50 (2) A permanent support (V) from the followingcomposition:

Nitrocellulose g 40 Tricresylphosphate g 10 Dicthylether cc-- 200Ethanol cc 700 n-Butanol cc 100 (3) A subbing layer (VI) from thefollowing composition:

Gelatin g 2 Water cc 17 Acetic acid cc-- 1 Methanol to cc-- 1000 (4) Anortho-chromatically sensitized silver chloro-- bromide emulsion (VII)with normal gradation and which does not contain hardeners at all.

Treatment 1 This light-sensitive material is rst exposed through agravure screen and then through a continuous tone diapositive.

Treatment 2 The exposed material is treated for 3 minutes in adevelopment solution of the following composition: Sodium sulfate(anhydrous) g-- 5 Sodium sulte (anhydrous) g-.. 20 Pyrocatechol g 6Pyrogallol g 8 1% solution of 6nitrobenzimidazole in methanol cc 8 Waterto oc 1000 Hereupon the developed material is immersed for 3 minutesinto a solution consisting of Sodium carbonate (anhydrous) g 170 Waterto cc- 1000 The developed material is then fixed for 5 min. in asolution consisting of Water cc 800 Sodium thiosulfate g 200 Potassiummetabisulte g 25 Water to M cc-- 1000 Treatment 3 After washing anddrying, the lm sheet is transferred, by pressing, onto a wetted copperplate.

Treatment 4 After 1 min. the temporary support is removed by stripping.

Treatment 5 A mixture consisting of Acetone cc 400 Ethanol cc-- 500Water cc 100 is poured onto the plate and after 15 sec. of action and 15sec. of drying at the air, the nitrocellulose membrane is stripped olf.

Treatment 6 The unhardened gelatin of the image layer is washed out withwarm water whereupon the subsisting resist is dried. The image areaswhich are not to be etched are covered.

Treatment 7 The plate is then etched with aqueous fcrric chloridesolutions as usual in gravure.

EXAMPLE 2 A stripping film is manufactured by successively applying thefollowing layers to the front side of a polyethylene terephthalatesupport (I) of 0.10 mm. thickness, the rear side of which is providedwith the usual photographic subbing (II) and antihalation layers (III):

(l) A stripping layer (IV) from the following composition:

Copolymer of vinylidenechloride and acrylonitrile g 20 Methylenechloride cc 250 Ethyl acetate cc 250 Acetone cc 530 (2) a permanentsupport (V) from the following composition:

Cellulosetriacetate g 40 Triphenylphosphate g 16 Methylene chloride cc500 Ethanol cc 250 Dichloroethane cc-- 250 (3) a subbing layer (VI) fromthe following composition:

(4) a silver chloro-bromide emulsion such as in Example 1.

This stripping lm is further exposed, developed and fixed as in Examplel.

After washing and drying, the film sheet is transferred by pressing ontoa wetted copper printing cylinder. After 1 min., the temporary supportis removed by stripping. The cylinder is then washed with a mixtureconsisting of:

Acetone cc 85 Methanol cc 'l0 Wat-er cc 5 AfterlS sec. of action thecylinder is dried for a short time in the air whereupon thecellulosetriacetate sheet is stripped -oif as a coherent membrane. Next,the gelatin image layer is washed out for 6 to 10 min. with an unheatedaqueous solution of sodium salicylate. After this washing period, theremaining gelatin relief is treated by pouring thereon an unheatedmixture consisting of ethanol (800 cc.) and water (200 ce), and quicklydried in a cold air current. Immediately thereafter the etching can bestarted.

We claim:

1. A process of making an etched printing member lby means of aphotographic light-sensitive stripping ilm, said lm having an unhardenedgelatino silver halide emulsion layer carried on a thin permanentsupport of cellulose ester containing about 5-40% by weight plasticizer,which support is adhesively joined to a temporary support by a strippinglayer, by the steps comprising:

(l) Exposing the emulsion `layer separately through a screen and to animage to be printed;

(2) Photographically developing the thus-exposed lm lby tanningdevelopment, fixing, and washing;

(3) Applying the iilm to a metal printing member by pressing the washed,developed gelatino layer there- `of into contact with the moistenedsurface of said member;

(4) Stripping the temporary support from the lm so applied while saidpermanent support and gelatino layer remain on said member;

(5) Infusilng the remainder of the ilm while in place `on the printingmember after step 4) with a liquid mixture containing by volume at leastabout 40% of a water-miscible organic ketone, which is a solvent forsaid permanent support, at least about 5% of water, and up to about of alower alkanol;

(6) Allowing the residual mixture remaining on the lm after step 5) toevaporate for a brief period until tight adherence as a coherent sheetof the permanent support of the gelatino layer is loosened;

(7) Forcibly peeling said permanent support from said emulsion layerwhile mantaining the layer not substantially above room temperature,leaving said emulsion layer intact;

(8) Washing unhardened gelatin from said gelatino layer to produce arelief image in hardened developed gelatin emulsion of the image to beprinted; and

(9) Applying an etching solution to the printing member carrying saidlrelief image to etch the image into the memiber surface.

2. The method of claim 2 wherein said cellulose ester is selected fromthe group consisting of cellulose acetate and cellulose nitrate, saidorganic ketone is acetone, and said alkanol contains up t-o two carbonatoms.

References Cited by the Examiner UNITED STATES PATENTS 2,614,93210/19'52 Nadeau et al. 96-83 X 2,650,877 9/1963 Boyer 96-83 X 2,805,9489/ 1957 Gerhardt et al. 96-83 2,892,711 6/1959 Sanford et al. 96-832,993,790 7/ 1961 Grumbine 96-35 3,057,722 10/1962 Alles 96--35 NORMANG. TORCHIN, Primary Examiner.

MILTON STEARMAN, Examiner.

1. A PROCESS OF MAKING AN ETCHED PRINTING MEMBER BY MEANS OF APHOTOGRAPHIC LIGHT-SENSITIVE STRIPPING FILM, SAID FILM HAVING ANUNHARDENED GELATINO SILVER HALIDE EMULSION LAYER CARRIED ON A THINPERMANENT SUPPORT OF CELLULOSE ESTER CONTAINING ABOUT 5-40% BY WEIGHTPLASTICIZER, WHICH SUPPORT IS ADHESIVELY JOINED TO A TEMPORARY SUPPORTBY A STRIPPING LAYER, BY THE STEPS COMPRISING: (1) EXPOSING THE EMULSIONLAYER SEPARATELY THROUGH A SCREEN AND TO AN IMAGE TO BE PRINTED; (2)PHOTOGRAPHICALLY DEVELOPING THE THUS-EXPOSED FILM BY TANNINGDEVELOPMENT, FIXING, AND WASHING: (3) APPLYING THE FILM TO A METALPRINTING MEMBER BY PRESSING THE WASHED, DEVELOPED GELATINO LAYER THEREOFINTO CONTACT WITH THE MOISTENED SURFACE OF SAID MEMBER; (4) STRIPPINGTHE TEMPORARY SUPPORT FROM THE FILM SO APPLIED WHILE SAID PERMANENTSUPPORT AND GELATINO LAYER REMAIN ON SAID MEMBER; (5) INFUSING THEREMAINDER OF THE FILM WHILE IN PLACE ON THE PRINTING MEMBER AFTER STEP4) WITH A LIQUID MIXTURE CONTAINING BY VOLUME AT LEAST ABOUT 40% OF AWATER-MISCIBLE ORGANIC KETONE, WHICH IS A SOLVENT FOR SAID PERMANENTSUPPORT, AT LEAST ABOUT 5% OF WATER, AND UP TO ABOUT 50% OF A LOWERALKANOL; (6) ALLOWING THE RESIDUAL MIXTURE REMAINING ON THE FILM AFTERSTEP 5) TO EVAPORATE FOR A BRIEF PERIOD UNTIL TIGHT ADHERENCE AS ACOHERENT SHEET OF THE PERMANENT SUPPORT OF THE GELATINO LAYER ISLOOSENED; (7) FORCIBLY PEELING SAID PERMANENT SUPPORT FROM SAID EMULSIONLAYER WHILE MAINTAINING THE LAYER NOT SUBSTANTIALLY ABOVE ROOMTEMPERATURE, LEAVING SAID EMULSION LAYER INTACT; (8) WASHING UNHARDENEDGELATIN FROM SAID GELATINO LAYER TO PRODUCE A RELIEF IMAGE IN HARDENEDDEVELOPED GELATIN EMULSION OF THE IMAGE TO BE PRINTED; AND (9) APPLYINGAN ETCHING SOLUTION TO THE PRINTING MEMBER CARRYING SAID RELIEF IMAGE TOETCH THE IMAGE INTO THE MEMBER SURFACE.